How to convert bigNumber array to int array?

Question

I have a smart contract method that return an array of uint256,

but when I console.log the result I got this :

[ BigNumber { s: 1, e: 1, c: [Array] } ]

How can we convert it to array of numbers? toNumber() work for a single object

Answer 1

Consider a deployed contract defined as follows:

pragma solidity ^0.4.25;
contract MyContract {
    uint256[] public data;
    function write(uint256 entry) public {
        data.push(entry);
    }    
    function read() public constant returns(uint256[]) {
        return(data);
    }
}

After having called write(1), write(3) and write(9), the expected outputs are as follows, depending on which web3 version is in use:

read() with [email protected]

MyContract.methods.read().call(function(error, result){
    if(!error) {
        console.log(result);
    }
});

Outputs:

[ '1', '3', '9' ]

read() with [email protected]

MyContract.read(function(error, result){                                                                                                                                    
    if(!error) {
        console.log(result);
    }
});

Outputs:

[ BigNumber { s: 1, e: 0, c: [ 1 ] },
  BigNumber { s: 1, e: 0, c: [ 3 ] },
  BigNumber { s: 1, e: 0, c: [ 9 ] } ]

As mentioned by user mirg, the results from the [email protected] call must be individually converted into a number or string.

Conversion example:

var array = [];
for(var i=0;i<result.length;i++){
    array.push(result[i].toString());
}
console.log(array);

Outputs:

[ '1', '3', '9' ]

Appendix

array100.js ([email protected])

const Web3 = require("web3");
const address = "https://rinkeby.infura.io/";
const web3 = new Web3(address);
const provider = web3.currentProvider;
const contractAbi=[{"constant":false,"inputs":[{"name":"entry","type":"uint256"}],"name":"write","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"read","outputs":[{"name":"","type":"uint256[]"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"data","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}];
const contractAddress = "0x0000000000000000000000000000000000000000";
var MyContract = new web3.eth.Contract(contractAbi, contractAddress);
MyContract.methods.read().call(function(error, result){
    if(!error) {                                                                                                                                                            
        console.log(result);
    }
});

array020.js ([email protected])

const Web3 = require("web3");
const address = "https://rinkeby.infura.io/";
const web3 = new Web3(new Web3.providers.HttpProvider(address));
const contractAbi=[{"constant":false,"inputs":[{"name":"entry","type":"uint256"}],"name":"write","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"read","outputs":[{"name":"","type":"uint256[]"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"data","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}];
const contractAddress = "0x0000000000000000000000000000000000000000";
var MyContract = web3.eth.contract(contractAbi).at(contractAddress);
MyContract.read(function(error, result){
    if(!error) {
        var array = [];
        for(var i=0;i<result.length;i++){
            array.push(result[i].toString());                                                                                                                               
        }
        console.log(array);
    }
});

Hope that helps.

Stay super!

/Javi